Police were called in and arrested 27 campaigners under Section 241 of the Trade Union Act after they began to release themselves shortly before 3pm yesterday, but not before they had halted traffic on Oil Sites Road since 6am.

SHAC spokesman Natasha Taylor said: 'We believe we have achieved a great deal through this protest.

'It has lasted nine hours and involved 34 individuals, which may well be a record, but that is nine hours that we have stopped product from leaving one of the biggest fuel suppliers in the country.'

And she added the campaign against the oil giant was far from over.

'We have a whole range of strategies up our sleeves and there is no doubt they will be deployed unless we receive an unequivocal statement from Shell saying they will not use Huntingdon Life Sciences,' she said.

'This action is just one part of a national campaign surrounding Shell that started six weeks ago. Shell should not underestimate the overwhelming public feeling about this subject.'

On the day before the first anniversary of the national fuel crisis, which started at the gates of Stanlow and ended up bringing the country to its knees, the national media descended on the site for the second time in a year.

SHAC supporters chained themselves across the main routes to the refinery using oil drums filled with concrete.

Oil Sites Road was closed for the safety of campaigners, some of who were lying in the road, police officers and other motorists.

At 10am yesterday there were 27 people, seven at the Boat Museum end, three at the junction with Bridges Road and 17 at the Hapsford end, cutting offall main routes to the site.

Traffic was gridlocked and police advised motorists to keep away from the surrounding roads.

The activists were calling for an end to Shell's involvement with HLS, which has bases in Cambridgeshire, Suffolk and New Jersey, USA.

During the protest SHAC spokesman Greg Avery said: 'Shell have a very public face and this protest is intended to bring what they are doing into the public light.

'We are out to financially and publicly damage any organisation that has connections with Huntingdon Life Sciences.

'We are in the business of highlighting not only Huntingdon Life Sciences but also any business that uses their filthy trade.'

One activist Sarah Hill, who was at the scene, said the aim of the protest was to close down HLS.

'We have a two-fold plan, firstly to get financial institutions to back away from supporting Huntingdon and we have had a huge amount of success in achieving this aim so far,' she said.

'Secondly to get customers who use the laboratory to stop these barbaric experiments.'

She claimed that in Shell s latest experiment they tested a plastic where animals were used in inhalation experiments.

'But Huntingdon have admitted their experiments don't often work and animals suffer needlessly,' said Ms Hill, who described herself as an animal rescue worker.

'Our message to Shell is clear and simple pull out of using animals in experiments.

'This is a political situation. We will remain here as long as it takes. Only the fire brigade have the equipment to move us as protesters are chained together inside drums of concrete. We know there are fire brigade officers present and eventually the police will have us moved.

'All the protesters are aware of the cosequences and we know we face arrest when the police decide to move us but we are prepared for that.'